1. FIELD OF THE INVENTION
The present invention relates to the problems of current gain fluctuations of bipolar transistors within integrated circuit semiconductor devices. More particularly, the present invention relates to a compensation current generator for generating a compensation current which is inversely proportional to the gain of a bipolar transistor, so as to compensate for current gain fluctuations of another bipolar transistor, which fluctuations can adversely affect the operation of the integrated circuit device which contains said bipolar transistors.
2. DESCRIPTION OF THE PRIOR ART
The current gain .beta., (termed "BETA") of a bipolar transistor can fluctuate, even when that transistor is driven by a constant current source. This current gain fluctuation is caused by process and/or temperature variations. Transistor deficiencies are typically circumvented in many transistor-circuit applications by maintaining the operating point of the transistors within some reasonable range, through the use of bias circuitry.
However, in some applications if nothing is done to provide more precise compensation for current gain fluctuations, the operation of a particular integrated circuit can be affected. In a semiconductor memory device, for example, current gain fluctuations can cause intolerable voltage fluctuations, with respect to a fixed reference voltage, resulting in reduced noise margin and, hence, faulty circuit operation. Thus, for these reasons, and others which will be explained more fully below, it is desirable to design a circuit in such a manner that compensation is provided, to a fixed reference voltage, for current gain fluctuations caused by temperature and/or process variations.